The drilling and production of a hydrocarbon reservoir requires the use of several types of oilfield fluids, such as but not limited to drilling fluids, completion fluids, production fluids, servicing fluids, and combinations thereof.
Drilling fluids are used in operations to drill boreholes into the earth; ‘drilling fluid’ is typically synonymous with ‘drilling mud’. One classification of drilling fluid is based on the composition of the fluid or mud. For example, water-based fluids, brine-based fluids, oil-based fluids and synthetic-based fluids, which are synthetically produced rather than refined from naturally-occurring materials.
Completion fluids are used to “complete” an oil or gas well for facilitating final operations prior to initiation of production, such as setting screens production liners, packers, downhole valves or shooting perforations into the producing zone. The fluid may help to control a well should downhole hardware fail, without damaging the producing formation or completion components. Completion fluids are typically brines (chlorides, bromides and formates), as long as the fluid is of proper density and flow characteristics. The fluid should be chemically compatible with the reservoir formation and fluids, and is typically filtered to a high degree to avoid introducing solids to the near-wellbore area. A regular drilling fluid is typically not suitable for completion operations because of their solids content, pH and ionic composition; however, drilling fluids may occasionally be suitable for both purposes.
Production fluid is the fluid that flows from a formation to the surface of an oil well. These fluids may include oil, gas, water, as well as any contaminants (e.g. H2S, asphaltenes, etc.). The consistency and composition of the production fluid may vary.
Servicing fluids, such as remediation fluids, workover fluids, and the like, have several functions and characteristics necessary for repairing a damaged well. Such fluids may be used for breaking emulsions already formed and for removing formation damage that may have occurred during the drilling, completion and/or production operations. The terms “remedial operations” and “remediate” are defined herein to include a lowering of the viscosity of gel damage and/or the partial or complete removal of damage of any type from a subterranean formation. Similarly, the term “remediation fluid” is defined herein to include any fluid that may be useful in remedial operations. These servicing fluids aid in balancing the pressure of the reservoir and prevent the influx of any reservoir fluids.
It is often beneficial to detect chemicals added to these fluids to monitor or determine a property of the oilfield fluid and/or the wellbore. These types of fluids may also be used to perform squeeze techniques where it is beneficial to force a treatment fluid or slurry into a planned treatment zone for further monitoring or detection of various properties. Such properties that may be monitored or detected may include, but are not limited to pH, dielectric constant, a chemical, an absorbance or emission at a given wavelength or integrals of wavelengths, magnetic property, and combinations thereof.
For example, determining the amount of the asphaltene inhibitors returning from a wellbore “squeeze” allows for determination of the “squeeze” lifetime and thus may act as a protection margin for the well against potential asphaltene deposition. The same is true for determining the use and/or amount of paraffin inhibitors, scale inhibitors, corrosion inhibitors, biocides, hydrogen sulfide scavengers, demulsifiers, reverse emulsion breakers, water clarifiers, drag reducers, and combinations thereof. Examples of suitable scale inhibitors may include, but are not limited to phosphinates, sulfonated polymers and copolymers, acrylic acid polymers and copolymers, phosphate esters, and the like.
Detecting these types of chemicals is often difficult because of the complexity of detecting such chemicals added to organic fluids or matrices with similar properties. That is, it is sometimes difficult to differentiate between added oilfield fluids.
It would be desirable if methods and compositions could be devised to better detect the presence, amounts and/or properties of the oilfield fluids and/or added chemicals typically used within the aforementioned fluids.